Metallizing gun for internal surfaces



Dec. 19, 1961 J. BLAND METALLIZING GUN FOR INTERNAL SURFACES 2Sheets-Sheet 1 Filed Sept. 50, 1957 1N VENTOR Julius Bland wan 0% AT TORA/E Y Dec. 19, 1961 J. BLAND 3,013,528

METALLIZING GUN FOR INTERNAL SURFACES Filed Sept. 30, 1957 2Sheets-Sheet 2 INVENTOR.

Jul/us Bland "3 ATTORNEY 3,013,528 METALLIZING GUN FOR INTERNAL SURFACESJulius Bland, Munster, Ind., assignor to Standard Oil Company, Chicago,iii., a corporation of lndiana Filed Sept. 30, 1957, Ser. No. 687,282 7Claims. (Cl. 1183tl2) This invention relates to a device for applyingsprayed metal to interior surfaces and, specifically, to a metallizingspray gun for applying sprayed molten metal uniformly to the internalsurfaces of non-rotatable cylindrical bodies, such as conduits, tubes,pipes, and the like.

One of the most successful and economical methods for minimizingcorrosion of conduits used for conveying corrosive gases or liquidswithout resorting to expensive alloys is to coat the internal surfaceswith a protective coating of material of substantially greater corrosionresistance. For many types of service, e.g., reformer furnace tubessubject to the corrosive action of high-temperature hydrogen sulfide ormixtures of hydrogen and hydrogen sulfide, and often alternate oxidizingand reducing atmospheres, it has been found particularly advantageous tocoat the internal tube surfaces with aluminum. Such coatings areconveniently applied by dipping the tube in, or otherwise filling thetube with, the protective metal in molten form. Alternatively, theinternal surfaces may be spray coated, or damaged protective coatingsmay be repaired, by use of commercially-available spray metallizingguns. Such guns are capable of supplying a relatively-fine spray ofmolten metal droplets. The gun is mounted Within the tube with thenarrow spray of molten metal directed at the surface. The tube iscontinuously rotated about its axis at a controlled rate so that thespray covers a complete arc of 360. Simultaneously, the gun is moved ata controlled rate parallel to the axis of the tube so that the tube maybe coated throughout its length.

in many cases, however, such as in the case of furnace tubes alreadyinstalled, it is not feasible to rotate the tubes. Furthermore, effortsto deflect a fine spray of molten aluminum outwards through a continuousarc of 360 and still obtain the desired metallic bonding have beenunsuccessful. Thus, prior art techniques such as conical diffusion discsand other solid or gaseous peripheral deflecting means which have provedsuccessful when spraying, for example, paints, resins, plastics and thelike are inoperative with line particles of molten metal. Such devicesor techniques cause plugging, non-uniformity and/or non-continuity ofthe coating, poor bonding and the like.

It is therefore an object of the present invention to provide anapparatus for applying sprayed metal uniformly to the internal surfacesof non-rotatable, cylindrical conduits, particularly tubes and pipes.Another object is to provide a simple device for spray metallizinginternal surfaces of conduits throughout their length and which may bereadily adapted to pipes of varying diameters. Another object is toprovide a metallizing spray gun for uniformly coating the internalsurfaces of nonrotatable tubes which is actuated by pressured gases.These and other objects of the present invention will be apparent as thedetailed description of the apparatus proceeds.

The invention resides in the discovery of a particular combination ofapparatus elements which successfully overcomes the many problemsinherent in the molten spray metallization of non-rotatable tubeinternals. The device comprises, in a simple embodiment, cylindricalnozzle means, said nozzle means containing a plurality of passagestherethrough for a continuously-fed rod of solid nited Stats atent spraymaterial and for combustible gases whereby said solid spray material maybe melted when said combustible gases are ignited adjacent to saidnozzle means; a heatconductive rotatable air cap concentric With andextendingbeyond said nozzles means and positioned with re spect to saidnozzle means so as to form an annular passage for channeling a first airblast toward the ignited gases and resulting melted spray of said meltedspray material, said rotatable air cap also containing an air outlet fora second air blast positioned so as to deflect said fine spray of saidmelted spray material away from the axis of said nozzle means; means forrotating said rotatable air cap at constant speed about the axis of saidnozzle whereby said fine spray of said melted spray material may bedeflected continuously through an arc of 360; and movable support meanswhereby said metalliz-ing spray gun may be moved with respect to saidnonrotatable cylindrical tube and in such a direction that the axis ofsaid spray nozzle and said non-rotatable cylindrical tube arecoincident.

The means for rotating the air cap is, conveniently, a driven gear, theaxis of which is coincident with the axis of said rotatable air cap andthe hub of which forms a collar around and is removably securable to atleast a portion of said rotatable air cap, and said driven gear isrotated by motor means, such as a compressedair-actuated motor, which ismounted on the movable support means and which is suitably coupled tothe driven gear. The coupling means may include flexible and/or rigid'shafting pinion-coupled to said driven gear.

The movable support means may comprise a hollow body member which isafiixed at one of its extremities to the nozzle means and which has aplurality of extendable support legs adjustably attached at their innerends to the body member and which have wheels, or other rotatable means,mounted at the outer ends in rolling contact with the inner surface ofthe tube to be sprayed. The plane of the wheels is, of course, parallelto the axis of the nozzle means. By adjusting the length of theextendable legs the metallizing spray gun is so positioned within thetube that the axes of the nozzle means and the tube coincide.

Combustible gases for melting the rod or wire of solid spray materialinclude mixtures of oxygen and acetylene, propane, natural gas, ormanufactured gas. In general, mixtures of oxygen and acetylene orpropane are preferred because of the higher heat contents. Ratio ofoxygen to the other gas depends on a host of variables includingcomposition of the other gas, type of spray metal, rate of feed of thecontinuously-fed spray metal, hardness of metal coating desired and thelike. As pointed out above, air may be used for restricting theresulting flame, for producing a fine spray of molten metal, and fordeflecting the resulting spray towards the side of the tube. It shouldbe understood, however, that the use of air is, in part, a matter ofconvenience and that other inert gases may also be used, e.g. nitrogen.In some instances, oxygen-free gases are preferred to minimize undesiredoxidation of the spray material. The air or other inert gas also servesto cool the various parts of ferred form of my spraying device showingdetails of the spray nozzle, rotatable air cap and means for rotatingthe air cap.

FIGURE 2 shows additional details of the device including otheraccessory equipment and the relationship of the assembled parts to eachother and to the tube being spray metallized; and

FIGURE 3 is an end view of the device, taken along line 3-3.

Referring to FIGURE 1, hollow body member 19 and body cap 11 with setscrews 12a and 12b comprise part of the movable support means shown infurther detail in FIGURE 2. Interior, and concentric with, said hollowbody member and body cap 11 is the nozzle means comprising nozzle body14 with insertable nozzle body adapter plate 41a, nozzle head 15, andnozzle clamp 16 which secures nozzle head to nozzle body 14.

Combustible gas tubes 17 and 19 and rigid tube 18 for the rod or wire ofspray metal extend the length of body member 19 and are connected tosaid nozzle body 14. Combustible gas tubes 17 and 19 are connected to acombustible gas supply to the left (not shown). Rigid spray metal feedtube 18 connects with a feeding means (not shown) which feeds a rod orwire of spray metal 20 through tube 18 and through said nozzle body 14and nozzle head 15. Rotatable air cap 21 (with front cover plate 21aremovably secured thereto) abuts against nozzle clamp 16 at surface 22so that it may be rotated around its common axis with nozzle head 15.Rotatable air cap 21 is held in place by means of body cap 11 which 24.gear 25, pinion 26, bushing 27, drive shaft 28, and

housing cover plate 29. Pinion 26 is rotated by drive shaft 28 which isflexibly coupled to a compressed-airactuated motor, which is shown inFIGURE 2. Gear 25, the axis of which is coincident with the axis ofrotataole air cap 21 and the hub of which forms a collar around and isremovably securable to said rotatable air cap by means of set screw 30,meshes with and is driven by pinion 26. Thus, when pinion rotates, gear25 turns rotatable air cap 21. Housing 24 is removably aflixed to bodycap 11 by means of housing clamp 31, which is tightened around body cap11 by means of set screws shown in FIGURE 2.

Hollow body member 10 contains compressed air, at elevated pressure,e.g., 50 to 150 p.s.i.g., which passes into annular space 32 surroundingthe nozzle means. This compressed air serves a number of purposes. Itpasses from annular space 32 into the annular space 33 and thus forms anannular air blast which converges towards the center line of the rod ofspray metal which extends to the right of nozzle head 15. This air blastrestricts the flame and produces a fine spray of molten metal. Anotherportion of the compressed air passes through passageway 3a in the upperpart of the rotatable air cap 21 and exhausts through an air outlet at35 which is positioned so as to deflect the fine spray of melted spraymaterial away from the axis of nozzle head 15, e.g., at an angle of Theair blast from both annular space 33 and from air outlet 35 also coolsthe surface being sprayed so that undue heating does not occur. Thecompressed air also forces the flange of rotatable air cap 21 againstbody cap 11 at bearing surface 23, thereby preventing any substantialescape of compressed air.

Contact at bearing surface 23 should, of course, be between non-scoringbearing metals which have a low coefficient of sliding friction. At thesame time, rotatable air cap 21 and metals in contact therewith shouldhave suliicicnt thermal conductivity to prevent overheating. To obtain alow coefficient of sliding friction at bearing surface 23, metals ofdissimilar hardness are used for body cap 11 and rotatable air cap 21.in general, a wide difference in hardness is preferred, limited, ofcourse, by the ability of the two metals to withstand the requiredloading. To assure rotation of air cap 21 with respect to body cap 11,outside diameter of the flange on air cap 2 1 must be less than theinside diameter of body cap 11 into which the flange fits, at alltemperatures encountered during the spraying operation. To assure suchclearance without excessive spacing the coefficient of thermal expansionof the metals should not be greatly dissimilar. In practice we havefound a rotatable air cap of bronze and a body cap of steel to be asatisfactory combination. Typically, the nozzle means, gear 25, pinion26, and bushing 27 may be brass, and housing 24, housing cover plate 29,and housing clamp 31 may be aluminum, thereby minimizing weight anddeflection of the apparatus.

During operation of the spray metallizing apparatus a rod or wire ofspray material 20 is continuously fed through tube 13. nozzle body 14and nozzle head 15, and is rapidly melted as it leaves nozzle head 15 bythe intense heat of combustion of combustible gases which enter thenozzle means via tubes 17 and 19, are mixed in annular space 36, and aredischarged from nozzle head 15 at multiple outlets 3'7 spaced evenlyaround nozzle head 25. Typically, one of tubes 17 and 19 contains oxygenat pressure while the other tube contains acetylene or propane gas. Theresulting molten metal is formed into a spray of finely-divideddroplets, e.g., 50 to 500 microns, by the air blast from annular space33. The finely-divided droplets are then deflected to the surface of theconduit being sprayed by the compressed air exhausting from air outlet35.

The rate of rotation of rotatable air cap 21, the feed rate of the rodof wire of spray metal, the selection of combustible gases and the likedepend upon a host of variables, such as the size of the wire, themelting rate of the wire, the thickness of the coating to be applied,

o and the like. For orientation, typical values when spray aluminizinginternal surfaces of steel furnace tubes, are a spray metal wirediameter of about to inch. This wire may be substantially-pure extrudedaluminum which is fed at the rate of about 25 to 500 feet per minute,e.g., 150 feet per minute. As pointed out hereinabove, the resultingmolten aluminum particles may range in size from about 50500 microns,e.g., 200 microns. Rotatable air cap 21 may be rotated at a rate up toabout revolutions per minute, e.g., about 35 revolutions per minute. Thespray apparatus may be loved along the axis of the tube being sprayed ata rate of about .1 to 10 feet per minute, e.g. 1 foot per minute. Thethickness of the resulting coating is typically in the range of about0.005 to 0.05 inch, e.g., 0.015 inch.

FIGURE 2 shows additional details with respect to the present inventionand how it would appear within conduit 41 which is being spraymetallized. Specifically, FIGURE 2 shows further details of the movablesupport means which comprises hollow body member 10, body cap 11, andbody bracket 38, which is bolted by bolts 38a and 3812, or otherwisefixedly secured, to body member 10 and on which is mounted a pluralityof extendable supporting legs 39 adjustably secured near their inner endto body bracket 33, and thus to body member 10. Wheels 40 are mountednear the outer end of extendable legs 39 and are in rolling contact withthe inner surface of conduit 41, as also shown in FIGURE 3. Length ofthe extendable legs 39 can be adjusted by loosening bolt 380 so thatextendable legs 39 may he slid in or out of a slot in an upraisedportion of bracket 38. By this means the center line of the nozzle meansand rotatable air cap are made to coincide with that of conduit 41.While in the present example only one body bracket with extendablesupporting legs is shown, it should be understood that the metallizingspray gun may use a series of such movable support means attached atconvenient intervals along the length of the body member 16.

FIGURE 2 also shows the compressed-air-actuated motor 42 with compressedair supply 42a mounted on body member If) by means of motor bracket 43.This motor drives shaft 28 by means of flexible coupling 44. As pointedout in connection with FIGURE 1, shaft 28 drives a pinion within housing24, which pinion in turn rotates gear 25 and thus rotatable air cap 21.While a flexible coupling 44, i.e., a wound-wire flexible shaft, is usedto couple motor 42 and shaft 28, it should be understood that coupling44 may, if the axes of motor 42 and shaft 28 coincide, be a rigid shaft.

No novelty is claimed in the means, per se, for feeding the wire ofspray metal 20 through tube 18 within body member Ill to the nozzlemeans, and thus such means is not shown in FIGURE 2. Such devices areavailable commercially (e.g., from the Metallizing Engineering Co.,Inc., Long Island City, New York) and can be obtained by consulting theappropriate equipment catalogs. Likewise, no novelty is claimed in themeans for moving the spray metallizing apparatus of the presentinvention at a constant rate along the axis of the conduit being sprayedand thus such means is also not shown in FIGURE 2. Such latter meanscould include a support for the means for feeding the wire of the spraymaterial, exterior of the conduit being sprayed, said support beingmoved at a constant speed by means of chain or worm drive in a directionparalleling the axis of the conduit. Preferably, both the means forfeeding the wire and the means for moving the unit along the length ofthe conduit are compressed-gas actuated, e.g., turbine motors driven bycompressed air. Thus, the entire apparatus may be mechanically operatedby the energy of compressed gas. This avoids the necessity, and possibledanger, of having another energy source, e.g., electricity, and othermotive means, e.g., electric-driven motors, present which wouldcomplicate the present apparatus.

In the case of compressed-air-actuated motor 42, the air exhausting fromsaid motor solves a problem heretofore unappreciated in the sprayaluminizing of tubes, particularly small diameter tubes. During suchoperation, the gun is withdrawn at a constant rate in a direction to theright of FIGURE 2, as rotatable air cap deflects the sprayed metalcontinuously through a 360 arc. Because of the confined space within thetube the dust inevitably stirred up by the spray metallizing operation,i.e., by impingement of the sprayed metal and gases, would coat surfacesnot yet metallized. In the present apparatus, however, the air exhaustfrom motor 42 forms a zone of positive pressure which tends to force thedust in a direction away from the spray nozzle, that is, to the left ofFIGURE 2. Thus, as a spray apparatus is moved progressively to the rightof FIGURE 2, any loosened dust or dirt is forced to the left and awayfrom the surface not yet metallized.

FIGURE 3 shows in better perspective how wheels 40 support the apparatussuch that the centerline of tube 41 and rotatable air cap .21 arecoincident. For tubes of larger diameter, the extendable legs containingwheels 40 would, of course, be lengthened. In like fashion, for smalldiameter tubes, the extendable legs would be shortened. The outer screwheads in FIGURE 3 are the means for fastening housing cover plate 29 tohousing 24. The inner screw heads in FIGURE 3 are the means forfastening the front cover plate of rotatable air cap 21. The dottedlines in FIGURE 3 illustrate how the hidden teeth of gear 29 mesh withthe teeth of hidden pinion 26.

Prior to and/or spray metallizing internal tube surfaces, otherpreparatory and/or finishing treatments might be used. For example, oil,grease and scale may be removed by pickling, flaming, sandblasting andthe like. The surfaces may then also be roughened by such techniques asgrit blasting and the like. Welding grooves, flange facings and othersurfaces which must not be aluminized may be masked. Information withrespect to such surface preparation may be obtained from standardmetallizing handbooks. After the surface has been metallized, additionaltreatments may also be employed, such as application of sealingmaterials, e.g., hydrolized ethyl silicate, aluminum pigmentedbitumastic or silicone vehicles, and the like. In the case of sprayaluminizing, an additional heat treatment to diffuse the aluminum intothe ferrous surface has been found to be advantageous. Such treatmentmight consist of heating the sprayed tube to a temperature of about 1275to 1300 F. for a period of about /2 hour. The sprayed surfaces may thenalso be brushed and air dusted.

While in describing the invention I have referred in detail to the form,arrangement and construction of parts, this is to be considered only inthe illustrative sense and I do not wish to be limited thereto, exceptas may be specifically set forth in the appended claims.

Having described my invention, I claim:

1. In a metallizing spray gun having nozzle means, said nozzle meanshaving a plurality of passages therethrough for a continuously-fed rodof solid spray material and for combustible gases whereby said solidspray material may be melted when said combustible gases are ignitedadjacent to said nozzle means, a heat-conductive rotatable air capconcentric with and extending beyond said nozzle means and positionedwith respect to said nozzle means to form an annular passage forchanneling an air blast toward the ignited gases and resulting meltedspray material and to produce thereby a fine spray of said melted spraymaterial, said rotatable air cap also having an air outlet meanspositioned to deflect said fine spray of melted spray material away fromthe axis of said nozzle means and onto a tube surface; the improvementenabling said metallizing spray gun to apply sprayed metal uniformly tothe internal surfaces of a non-rotat able cylindrical tube whichcomprises means inserta'ble within said cylindrical tube for rotatingsaid rotatable air cap at constant speed about the axis of saidnonrotatable cylindrical tube whereby said fine spray of said meltedspray material may be deflected continuously through an arc of 360, saidmeans comprising a motor means and a gear driven by said motor means,the axis of said gear being coincident with the axis of said rotatableair cap and the hub of said gear forming a collar around and beingremovably securable to at least a portion of said rotatable air cap, andadjustable support means whereby said metallizing spray gun may be movedaxially with respect to said non-rotatable cylindrical tube and in sucha direction that the axis of said rotatable air cap and saidnon-rotatable cylindrical tube are coincident.

2. The metallizing spray gun of claim 1 wherein said 7 motor means is acompressed-gas-actuated motor mounted on said adjustable support meansand flexibly coupled to said driven gear.

3. In a metallizing spray gun having nozzle means, said nozzle meanshaving a plurality of passages therethrough for a continuously-fed rodof solid spray material and for combustible gases whereby said solidspray material may be melted when said combustible gases are ignitedadjacent to said nozzle means, a heat-conductive rotatable air capconcentric with and extending beyond said nozzle means and positionedwith respect to said nozzle means to form an annular passage forchanneling an air blast toward the ignited gases and resulting meltedspray material and to produce thereby a fine spray of said melted spraymaterial, said rotatable air cap also having an air outlet meanspositioned to deflect said fine spray of melted spray material away fromthe axis of said nozzle means and onto a tube surface; the improvementenabling said metallizing spray gun to apply sprayed metal uniformly tothe internal surfaces of a non-rotatable cylindrical tube whichcomprises means insertable within said cylindrical tube for rotatingsaid rotatable air cap at constant speed about the axis of saidnon-rotatable cylindrical tube whereby said fine spray of said meltedspray material may I e deflected continuously through an arc oi 360; andadjustable support means whereby said metallizing spray gun may be movedaxially with respect to said non-rotatable cylindrical tube and in sucha direction that the axis of said rotatable air cap and saidnonrotatable cylindrical tube are coincident, said adjustable supportmeans comprising a hollow body member affixed at one extremity to saidnozzle means, extendable legs adjustably attached at their inner ends tosaid body member and having wheels mounted at their outer ends inrolling contact with the inner surface of said non-rotatable cylindricaltube whereby adjustments to the length of said extendable legs positionsaid metallizing spray gun within said non-rotatable cylindrical tube sothat the axes of said rotatable air cap and said non-rotatablecylindrical tube coincide.

4. In a metallizing spray gun for applying sprayed metal uniformly tothe internal surfaces of a non-rotatable cylindrical tube whichcomprises in combination a. hollow body member wholly insertable in saidnon-rotatable cylindrical tube, the hollow interior of said body memberproviding passages for compressed air, for a continuously-fed rod ofsolid spray material, and for at least one conduit containingcombustible gases capable of melting said solid spray material whenignited; nozzle means at one extremity of said hollow body member andhaving a common axis therewith, said nozzle means containing a pluralityof passages therethrough for said continuously-fed rod of solid spraymaterial and for said combustible gases whereby said solid spraymaterial may be melted when said combustible gases are ignited adjacentto said nozzle means; and a heat conductive rotatable air cap concentricwith and extending beyond said nozzle means in a direction away fromsaid body member and positioned with respect to said nozzle means toform an annular passage for channeling an air blast toward the ignitedgases and resulting melted spray material andto produce thereby a finespray of said melted spray material, said rotatable air cap also havingan air outlet positioned to deflect said fine spray of melted spraymaterial away from the axis of said nozzle means and onto the surface ofthe non-rotatable cylindrical tube, said rotatable air cap also havingan external cylindrical flange held in bearing contact with said bodymember by the pressure of said compressed air in said body member; theimprovement comprising a plurality of extendible supporting legsadjustably secured near their inner end to said body member and havingwheels mounted near their outer end in rolling relationship with theinterior surface of said non-rotatable cylindrical tube, and motor meanscarried by said body member and connected by coupling means to saidrotatable air cap to rotate said rotatable air cap at a constant ratearound the common axis of said nozzle means and said rotatable air cap.

5. The metallizing spray gun of claim 4 wherein said motor means is acompressed-air-actuated motor.

6. The metallizing spray gun of claim 4 wherein at least the metals ofsaid rotatable air cap and said body member which are in bearing contactare non-scoring bearing metals.

7. In a metallizing apparatus for uniformly applying a spray of finelydivided molten aluminum to the internal surface of a non-rotatablecylindrical tube which comprises in combination a hollow cylindricalbody member, the hollow interior of said body member providing a passagefor compressed air, for a plurality of conduits containing combustiblegases capable of melting aluminum when ignited, and for a conduitadapted to receive aluminum wire, said aluminum wire being continuouslyfed by a first compressed-air-actuated driving means exterior of saidtube; cylindrical nozzle means at one extremity of said hollow bodymember and having a common axis therewith, said nozzle means having aplurality of passages therethrough for said aluminum wire and for saidcombustible gases whereby said aluminum wire may be melted when saidcombustible gases are mixed and ignited adjacent to said nozzle means;and a heat-conductive rotatable air cap concentric with and extendingbeyond said nozzle means in a direction away from said body member andpositioned with respect to said nozzle means to form an annular passagefor channeling a first air blast toward the ignited gases and theresulting molten aluminum and to produce thereby a spray of finelydivided molten aluminum, said rotatable air cap also having an airoutlet for a second air blast positioned to deflect said fine spray offinely-divided molten aluminum away from and at a preselected angle tothe axis of said nozzle means and onto the surface of the non-rotatablecylindrical tube, said rotatable air cap also having an externalcylindrical flange held in bearing contact with said body member by thepressure of said compressed air in said body member, whereby saidrotatable air cap may rotate with respect to said body member withoutsubstantial leakage of said compressed air at the bearing contactsurfaces; the improvement comprising a plurality of extendiblesupporting legs adjustably secured near their inner ends to the exteriorof said body member and having wheels mounted near their outer ends inrolling contact with said internal surface of said non-rotatablecylindrical tube, and a second compressed-air-actuated motor fixedlymounted on said body member adjacent to said nozzle means and connectedby coupling and 'gear means to said rotatable air cap to rotate saidrotatable air cap at a constant rate around the common axis of saidnozzle means and said rotatable air cap, said secondcompressed-air-actuated motor being insertable in the non-rotatablecylindrical tube.

References Cited in the file of this patent UNITED STATES PATENTS1,725,012 Meurer Aug. 20, 1929 1,942,876 Perkins Jan. 9, 1934 2,088,348Schlupmann July 27, 1937 2,340,903 Shepard Feb. 8, 1944 2,560,411 BurnsJuly 10, 1951 2,769,663 Jensen et al Nov. 6, 1956 2,800,875 Jewell July30, 1957 2,845,366 Schroeder July 29, 1958 2,865,321 Von Arx Dec. 23,1958

